August 2015

Ultra-Low Power Wireless SoCs Enabling a Batteryless IoT

Dr. Benton Calhoun and Dr. David Wentzloff co-CTOs

©PsiKick 2015 2

Today’s IoT… is messy

The “Internet of Things”

Figure from venturescanner.com

©PsiKick 2015 3

Today’s IoT… is limited by hardware

Most wireless IoT devices use:  … MCU at 10s of MHz and 1s of mA  … Radio at 5-10s of mA (e.g. BLE)  … Battery  … Active power in 10s to 100s of mW  … Achieve “Low Power” by duty cycling, or

turning OFF for large fractions of time  Limited in functionality or lifetime

©PsiKick 2015 4

Next Wave of Computing: “Internet of Things”

1960s

1980s

1990s

2010s

2000s

2015

2025: 1 trillion wireless sensors

2020: 50 billion connected devices

Today’s IoT Devices –

NOT going to get

us to 1 Trillion

©PsiKick 2015 5

Powering 1 Trillion Sensors...

BATTERIES

 Today’s RF ICs = 10s to 100s mW ACTIVE

 with current batteries 

hours/days/months

 No “Moore’s Law” for energy density

 1T x 10 yr. batteries = 275M

replacements/recharges per day

 THE ANSWER, but...

 It only delivers 10s of µWs / cm2

 Versus 10s to 100s of mWs

 Need 2-3 order of magnitude

improvement

 So, power target of 20-30 µWs

Need wireless SoCs @ 1/1000th of today’s power consumption

Piezo

Indoor Solar

Thermal Gradient

RF Induction

ENERGY HARVESTING

©PsiKick 2015 6

Harvested Power = PHARV(t)

Consumed Power

= PLOAD(t)

Estorage (cap)

PLOAD may exceed PHARV for some time periods

Constraint on power used over any time period:

Good: PHARV ↑ Estorage↑ PLOAD ↓

VKILL EUSABLE

dttPtPEt HARV

t

LOADUSABLE )]()([, 0

 

Self-powered Operation

©PsiKick 2015 7

Power Limitations for IoT

Harvestable power: ~10s of µW/cm2

©PsiKick 2015 8

Power Limitations for IoT

ACTIVE power today: ~1s to 100s of mW

Harvestable power: ~10s of µW/cm2

©PsiKick 2015 9

Power Limitations for IoT

ACTIVE power today: ~1s to 100s of mW

Harvestable power: ~10s of µW/cm2

Need to reduce power active power by ~1000X to < 20-30µW

©PsiKick 2015 10

What can you do with 20 – 30 µW ACTIVE power?

©PsiKick 2015 11

Agenda

 Proof of Concept: Self powered University SoCs  Self-powered Wakeup Radio  Self-powered SoC for the IoT

©PsiKick 2015 12

What can you do with 20 – 30 µWs? A lot.

19 µW Wearable ECG / EEG / EMG 6.46 µW Wireless Activity Monitor

 Activity Monitor Demo:  3-axis accelerometer data  Extract posture, activity  Build histogram of activity Stream

raw data over TX (10m range)

 Harvest from PV with MPP tracking and 75% efficiency end-end

 No battery

 6.46 µW total power  ISSCC 2015

 Wearable ExG  Continuous ECG  Extract heart rate intervals  Detect atrial fibrillation  RF updates every ~3-5s  Powered by body heat with

Thermoelectric Generator  No battery

 19 µW total ACTIVE power  ISSCC 2012

©PsiKick 2015 13

Digital Sub- Threshold Circuit

Operation

 Low-voltage, sub- threshold digital circuits

 Devices are “off”, resulting in 10X power savings

Low-Power RF Expertise

 Extremely low power radio frequency

 10+ years developing low-power/high- performance RF

System-level Integration

 Tight system integration dramatically improves efficiency

 “Un-blocks”

 Understand and optimize for lowest joules per operation

Approach to Achieving Ultra Low Active Power

Key breakthroughs in...

…resulting in a new paradigm of circuit design

Trade-offs

 RF Range – sweet spot between 1 m and 4 km; data rate between 1 Mb/s and 1 kb/s

 Processor Speed – sweet spot between 100s kHz and 10s MHz

©PsiKick 2015 14

Agenda

 Proof of Concept: Self powered University SoCs  Self-powered Wakeup Radio  Self-powered SoC for the IoT

©PsiKick 2015 15

Self Powered Wakeup Chip (PK1001) Application

Existing

IoT Device

(Main RF Chipset)

PK1001 GO!

PK1001 powered from

a harvested energy

source and charges an

energy storage device

RF signal addressing

detected. PK1001

issues interrupt to

Main RF chipset

1

Main RF chipset

communicates with

handset. Decides when

to go to sleep

2 3

http://www.google.com/url?sa=i&rct=j&q=&esrc=s&frm=1&source=images&cd=&cad=rja&docid=CwHZWChOSuix_M&tbnid=bW44k_uLQvvtjM:&ved=0CAUQjRw&url=http://mermodynamics.com/calmdown/iphone.html&ei=QyMcUsf3NbPH4APouoGgAQ&psig=AFQjCNGVKuZk00tlvp9Vq1ZbqM7xMM-6KA&ust=1377662109854638 http://www.google.com/url?sa=i&rct=j&q=&esrc=s&frm=1&source=images&cd=&cad=rja&docid=U1PMMvIVgqzu2M&tbnid=dYIFAInULDTUYM:&ved=0CAUQjRw&url=http://www.clker.com/clipart-wireless-antenna-1.html&ei=gyQcUprDOu364AOxi4HwAw&bvm=bv.51156542,d.dmg&psig=AFQjCNGQXGMQu8OuE9jr3-RGsv08alVrOw&ust=1377662444568646 http://www.google.com/url?sa=i&rct=j&q=&esrc=s&frm=1&source=images&cd=&cad=rja&docid=5X4_VGlpbE3eDM&tbnid=uDkl02tAfOSLTM:&ved=0CAUQjRw&url=http://www.psdgraphics.com/psd-icons/battery-levels-icons/&ei=oSYcUrzcGrH94AOO1IGIBw&psig=AFQjCNEIwyu_-PaPeXIX6kslJu-mEvgv0g&ust=1377663000139374 http://www.google.com/url?sa=i&rct=j&q=&esrc=s&frm=1&source=images&cd=&cad=rja&docid=BeX7FLDlZzMoJM&tbnid=vd8B_n0_AoLCnM:&ved=0CAUQjRw&url=http://www.northcoastirwmp.net/Content/10369/2/Solar.html&ei=uCEcUo__H5P84AP1kYGICA&bvm=bv.51156542,d.dmg&psig=AFQjCNFwZXkdYuQt6YY3BsLMB5T0Ib4nDw&ust=1377661735336939 http://www.google.com/url?sa=i&rct=j&q=&esrc=s&frm=1&source=images&cd=&cad=rja&docid=U1PMMvIVgqzu2M&tbnid=dYIFAInULDTUYM:&ved=0CAUQjRw&url=http://www.clker.com/clipart-wireless-antenna-1.html&ei=gyQcUprDOu364AOxi4HwAw&bvm=bv.51156542,d.dmg&psig=AFQjCNGQXGMQu8OuE9jr3-RGsv08alVrOw&ust=1377662444568646

©PsiKick 2015 16

PK1001 Main Features

 World’s lowest-power wake-up radio solution – A self-powered wireless trigger – ~500nW ACTIVE system power measured

• No radio duty cycling – 3-7 meter wireless range – Retrofit existing IoT devices to reduce power from mW to

©PsiKick 2015 17

Block Diagram of Wakeup Radio Chip

Clock generation

psikick

Multiple VDDs 0.5V, 1.0V, 2.5V

Off-chip battery Or cap

SPI Slave

Regulator Interrupt Handler

Boost converter

Harvesters

Clock out

Clock ext

VDDs

PMU

4b

INT_OUT

32.768 kHz XTAL

RF

ULP RX (path 1,2)

BLE Wakeup RF harvest

INT_IN 31b Code Wakeup

Data processing

Counters

Memory Mapped Register File

Reset Handler

General Purpose Driver

RESET_BAR

GPD

©PsiKick 2015 18

Block Diagram of Wakeup Radio Chip

Clock generation

psikick

Multiple VDDs 0.5V, 1.0V, 2.5V

Off-chip battery Or cap

SPI Slave

Regulator Interrupt Handler

Boost converter

Harvesters

Clock out

Clock ext

VDDs

PMU

4b

INT_OUT

32.768 kHz XTAL

RF

ULP RX (path 1,2)

BLE Wakeup RF harvest

INT_IN 31b Code Wakeup

Data processing

Counters

Memory Mapped Register File

Reset Handler

General Purpose Driver

RESET_BAR

GPD

Clock Gen: 32kHz clock with counters for interrupt generation and time keeping

©PsiKick 2015 19

Block Diagram of Wakeup Radio Chip

Clock generation

psikick

Multiple VDDs 0.5V, 1.0V, 2.5V

Off-chip battery Or cap

SPI Slave

Regulator Interrupt Handler

Boost converter

Harvesters

Clock out

Clock ext

VDDs

PMU

4b

INT_OUT

32.768 kHz XTAL

RF

ULP RX (path 1,2)

BLE Wakeup RF harvest

INT_IN 31b Code Wakeup

Data processing

Counters

Memory Mapped Register File

Reset Handler

General Purpose D